Caffeine is a partially water-soluble alkaloid. The removal of caffeine from natural products such as coffee beans, cocoa beans and tea leaves has resulted in the multibillion dollar decaffeinated beverage industry.
The rise of decaffeinated beverages has resulted in part from the health concerns of ingesting excessive amounts of caffeine. Caffeine stimulates the nervous system. Excessive amounts of caffeine can make people tense, irritable, unable to sleep, and, in some cases, elevate the heart rate to unsafe levels. Caffeine can also irritate the alimentary canal. It is common for people diagnosed with sensitive stomachs, colons and the like to be required, as part of their medical treatment, to refrain from ingesting caffeine.
Generally, caffeine has been removed directly from green or roasted beans or from caffeine-containing liquids by dissolving the caffeine in water or organic solvents or passing the caffeine-containing liquid over an ion exchange resin which attracts the caffeine. For example, L. Klein, U.S. Pat. No. 1,039,961 discloses a process for decaffeinating coffee beans by employing mixtures of two or more alkali solvents. E. Burgen, U.S. Pat. No. 2,198,859 discloses heating raw coffee beans with water in the presence of an adsorption agent, such as activated carbon. H. Grossman, U.S. Pat. No. 2,375,550 employs selective adsorbents such as hydrated silicates to remove caffeine.
H. Turken et al., U.S. Pat. No. 3,108,876 teach passing a coffee concentrate over an ionic exchange resin such as polystyrene sulfonic acid resins, carboxylic acid resins, and polystyrene quaternary amine resins. G. Margolis et al., U.S. Pat. No. 4,031,251 disclose a decaffeination process using a non-ionic hydrophobic resin contacted with an aqueous extract of vegetable material.
S. Katz, U.S. Pat. No. 4,113,886 discloses a process which permits caffeine to diffuse through a porous, hydrophilic membrane using a water-immiscible caffeine-specific solvent with a water phase on the opposite side of the membrane. G. van der Stegen, U.S. Pat. No. 4,364,964 discloses a process for removing caffeine from green coffee beans using a synthetic resin which is produced by a polymer containing aromatic ring systems and polar acidic groups.
Each of these methods suffer from a number of disadvantages. None of the cited methods of decaffeinating a liquid are particularly adapted to producing a decaffeinated beverage in the home. Water and organic solvent employing systems must be performed in a commercial processing facility which adds to the cost of producing the beverage and requires that decaffeinated beverages must be sold separately packaged from caffeinated beverages (e.g. decaffeinated coffee products are sold separately from caffeinated coffee products). In addition, organic solvent systems are disadvantageous because of the environmental concerns of using such chemicals.
The third method, employing synthetic resins to attract the caffeine in a caffeinated beverage, eliminates the use of costly solvent systems. However, the degree of attraction of the caffeine for the resins is limited and therefore such systems do not efficiently remove caffeine from caffeine-containing liquids.
With the increasing market for decaffeinated beverages, it would be a significant advance in the art to provide an effective method of decaffeinating liquids without using solvents. It would be particularly advantageous if such a system could be incorporated into a consumer appliance, such as a coffee maker, to make a decaffeinated beverage in the home.